Automated brewing machines for brewing beverages such as coffee and tea, also known as on-demand systems, usually have a brewing water reservoir in which water is heated by a heating element. The heated water is then transferred from the reservoir to a brewing chamber which contains the brewing ingredients, such as coffee grounds or tea leaves, through which the heated water flows to produce a brewed beverage. The beverage flows into a container such as a jug or cup located beneath the brewing chamber outlet.
Many modern domestic beverage machines dispense individual servings of a beverage directly into a drinking receptacle, and derive the beverage either from a bulk supply of beverage ingredients or from individual packages of beverage ingredients such as pods, pads or cartridges. Machines which use such packages reduce the need for cleaning and can enable the user to make a selection of beverages such as coffee, tea, hot chocolate and the like as well as food products such as soup, custard and the like. The beverages are formed from brewing, mixing, dissolving or suspending the beverage or food ingredients in water. For example, for coffee beverages, heated water is forced through the package under pressure to extract the aromatic constituents from the compacted coffee grounds contained therein. The use of packages in such machines has become increasingly popular due to their convenience and the quality of the beverage produced.
EP-A-0904717 describes a package in the form of a soft flexible pod or pouch which is made from two discs of filter paper which are connected around their perimeters by a seam. The pod is designed so that hot water can be fed under pressure and passed through the pod which is filled with the beverage ingredients. However a significant problem with this type of soft pod lies in that its shape and design is not ideal to enable the flow of water through the pod to be accurately controlled. The pod of EP-A-0904717 therefore requires the use of a specially designed container in which the pods are placed before they can be used in the beverage machine.
This problem can be overcome in more rigid packages such as the cartridges described in EP-A-1440903. This type of cartridge is formed from high density polyethylene, polypropylene, polystyrene, polyester, or a laminate of two or more of these materials. The cartridge has an inlet for the introduction of water into the cartridge, and an outlet for a beverage produced from the beverage ingredients. The cartridge comprises an outer member, an inner member inserted in the outer member and an aperture in a beverage flow path linking the inlet to the outlet for producing a jet of the beverage. In order to optimise the quality of some types of beverage it is necessary to maximize the extraction of the beneficial flavours of the beverage ingredients (such as coffee), while minimizing the extraction of bitter compounds and undesirable components. This is achieved by optimising a number of different brew parameters. It is acknowledged, by discerning coffee drinkers, that coffee produced using water which is cooler than the optimum temperature tastes sour and that produced with water which is hotter than this temperature tastes bitter. The sour taste, which occurs if the temperature is too low, is due to under extraction, since the acids from the beans are the first substances to dissolve. The optimum temperature for espresso is claimed, by some baristas to be between 92 and 96° C. Other factors which affect the quality of coffee include the roasting and age of the coffee beans, the grind size, the compaction of the grinds prior to brewing, and the brew time. The highest quality coffee is achieved by balancing these key elements of the brewing process.
Different flow rates of the brewing water (or other liquid) through an on-demand beverage machine will therefore lead to a variation of characteristics in the brewed beverage, and in particular to its taste. U.S. Pat. No. 5,901,635 explains that a relatively fast rate of flow of hot water through coffee grounds in the brewing chamber will result in relatively dilute coffee with less flavour and caffeine than is produced by a slower rate of flow. A relatively slow rate should therefore be used in order to correctly brew a decaffeinated coffee drink with a taste comparable to “regular” or caffeinated coffee which is brewed with a relatively faster rate of flow. The flow rate can he determined by a number of variables, such as the rate at which water is introduced to the reservoir, the size of the conduit or passage between the reservoir and the brewing chamber, and the size of holes in a water distributor or showerhead over the brewing chamber. U.S. Pat. No. 5,901,635 uses an adjustable valve between the filling chamber and the reservoir to adjust the rate of flow of water from the filling chamber to the reservoir.
WO-02/074661 describes a device for preparing customisable brewed beverages and proposes the use of two ingredient extraction chambers each containing a different volume of ingredients, such as roast and ground coffee. The strength of the finished brewed beverage can be modified by directing the brewing fluid through one or other of the chambers, or dividing the flow to go through each chamber. In another embodiment described in this prior art document, different ingredients are provided in different chambers.
However most on-demand machines typically have a preset non-variable water flow rate and temperature. It is therefore desirable to find other ways of modifying at least one preparation parameter to change the characteristics, preferably to improve the quality, of the beverage or food product. This is particularly desirable for machines which use soft pods, through which it is more difficult to control the water flow than rigid cartridges.